Metal laminates and method of forming by electroplating



Nov. 29, 1966 A. H. DU ROSE ETAL 3,238,574

METAL LAMINATES AND METHOD OF FORMING BY ELECTROPLATING Filed April 10,1964 CORROSION CHROA/IIUM PLATE BRIGHT NICKEL PLATE IIIPLEAIEEALEAEQLLIEE NICKEL PLATE F/ BRIGHT NICKEL PLATE NICKEL-ARSENIC ALLOYPLATE (0. 0/-o.2 M/L., O.25%-8% ARSEN/C) NICKEL PLATE METAL BASECORROSION CHROMIUM PLATE V/l VT /7\4/ s\\ w R L/ BRIGHT NICKEL PLATENICKEL-ARSENIC ALLOY PLATE R I- 0-2 M/L., 0.25-8'Z ARSEN/C) NICKEL PLATEMETAL BASE FIG} ARTHUR H. DUROSE AND WJLLIAM J. PIERCE, INVENTORSATTORNEY United States Patent Office 3,283,5'3'4 Patented Nov. 29, 19663,288,574 METAL LAIVHNATES AND NHETHUD 6F FGRPv HNG BY ELECTROPLATINGArthur H. Du Rose, Euclid, and William 3. Pierce, Lyndhurst, Qhio,assignors to The Harshaw Chemical Company, Cleveland, Ohio, acorporation of Ohio Filed Apr. 10, 1964, Ser. No. 358,872 20 Claims.(Cl. 29-194) This invention relates to a composite coating of threeadjacently bonded layers of nickel and more particularly this inventionrelates to such a composite coating wherein the intermediate layerthereof comprises a thin nickel deposit containing a desired amount ofarsenic.

In recent years much work has been done to provide an article with adecorative plate of chromium over two or three underlying layers ofnickel. The composition and electrochemical properties of these layersof nickel are balanced to obtain good protection of the base surfaceagainst corrosion without compromising the decorative appearance. To beeffective the series of nickel layers must be deposited from platingbaths adapted to impart not only the desired electrochemical propertiesto the nickel layers but also the other physical and chem icalproperties necessary for a good plate. Moreover, thebrightness and othersurface characteristics of the top layer must be such that the chromiumdeposit be smooth, lustrous and substantially free from color, spots andthe like.

When using three layers of nickel, the composition of the intermediatelayer is adjusted so as to be anodic to both the upper agnd lower layersand preferably the composition of the upper layer is adjusted so as tobe anodic to the lower layer. The decorative chromium layer is morenoble than the said nickel layers. Moreover, the intermediate layeradvantageously is made very thin, the reasons for which will beexplained more fully hereinafter.

Originally, the triple-layer systems were made using as the intermediatelayer metals usually different from nickel but anodic thereto. With theuse of some systems, marked corrosion protection was observed (seeKnapp, Trans. Inst. Met. Finishing, 1958, 35, 139-165). In most cases,however, the systems were found not to be useful, either because themetal corroded too rapidly causing blistering or scaling or because themetal stained or colored the decorative surface.

Within the last few years triple-layer systems have been made using anickel-containing deposit for each layer and wherein relative potentialsof the layers are controlled by the amounts of sulfur deposited with thenickel. The sulfur may be controlled in the bath by adjusting thecontents of the various organic brightening additives comprising sulfurwith o-r without additional sulfur-containing compounds. Sulfur-freebrighteners with sulfo-oxygen carriers also may be used to enhance thesulfur in the nickel deposit. This control of the addition agentsultimately controls the amount of sulfur in the electrodeposits andthereby the relative potential which is considered to be the importantfactor.

Several problems have confronted the industry in accepting thetriple-layer system because sulfur as such not only provides differencesin potential in electrodeposits of nickel but also affects otherphysical properties such as ductility and brightness and continuity ofthe deposit. For instance, if the proper potential is to be maintainedbetween the intermediate layer and the top layer, the sulfur contents ofeach layer must be controlled. However, there is evidence that theelectronegative potential (its relative susceptibility to corrosion) ofsulfur-containing nickel does not vary as a straight line function inrelation to the sulfur content and tends to level off at sulfurconcentrations in the range of from about 0.2-0.3 percent by weight.Thus it is seen that the degree in which the concentration of sulfur maybe varied in the nickel layer to adjust potential is very narrow.Moreover, if a manufacturer prefers to deposit a lower layer of nickelfrom a sulfur-containing bath, he necessarily will have to increase theamounts of sulfur in the intermediate and upper nickel layersnecessitating the adjustment of the other additives in the bath.

It has now been discovered that triple layer systems usingarsenic-containing intermediate layers are not only more durable thanthe systems using sulfur in the intermediate layer but they are moreeasily and advantageously prepared; they may be deposited merely from astandard bath having the proper concentration of a water-soluble arseniccompound. Moreover the arsenic compounds are more stable in the baththan the sulfur compounds which may be used in the bath to impart sulfurinto the deposit especially in regard to air oxidation, thus permittingair agitation to any degree desired.

in accordance with the present invention there is provided an improvedcomposite coating comprising three adjacently bonded layers of nickeldeposits, the lower layer of a conventional low-sulfur nickelelectroplate preferably 0.3 to 2 mils thick and having from 0 to about25 percent cobalt by weight alloyed therewith and a sulfur contentpreferably less than 0.01 percent, a top layer of a conventional brightnickel electroplate preferably 0.15 to 1 mil thick and having from 0 to50 percent cobalt alloyed therewith and preferably from about 0.03percent to about 0.3 percent sulfur by weight; and characterizing theinvention, an intermediate layer 0.01 to 0.2 mil thick of whichcomprises a deposit of nickel having from about 0 to about 25 percentcobalt alloyed therewith and containing from about 0.025 percent arsenicto about 8 percent arsenic based on the total weight of said deposit.

For reasons to be explained more fully hereinafter, the triple-layercomposite coatings of the present invention are generally moreadvantageously prepared using intermediate layers having arsenicconcentrations in the range of from about 0.25 percent to about 4percent. More preferably the arsenic concentration is kept in the rangeof from about 0.50 percent to about 2.5 percent.

The mechanism by which the triple-layer coating system of the presentinvention acts to protect a corrodible substrate is more easilyunderstood by referring to the accompanying drawing in which:

FIG. 1 illustrates schematically a triple-layer system with a corrosionpit in its incipient stage.

FIG. 2 illustrates the same triple-layer system with the corrosion pitin an advanced stage where the pit has reached and has attacked theintermediate layer.

FIG. 3 illustrates the same triple-layer system with the corrosion pitwidened laterally but where the lower layer has not been attackedsubstantially.

The composite electroplate of the present invention advantageously isemployed over various substrates and particularly substrates susceptibleto corrosion. Iron, steel, copper, brass, aluminum, zinc and magnesiumwith or without a copper deposit, are substrates protected by thecomposite electroplates of the present invention.

The arsenic present in the intermediate layers of the instanttriple-layer composites provides surprisingly good corrosion protect-ionto the substrate covered by the system. The electroplate composites ofthe present invention are three to four times more effective than thoseprepared using sulfur in the intermediate layer. The projected rust-freelife of the instant composite may approach 5-6 years, based on theresults of the standard Corrodkote and CASS corrosion tests. Thecorresponding triple-layer composites having sulfur-containingintermediate layers have at best a 2 to 4 year projected rustfree lifebased on these tests.

Corrodkote is the name given to an accelerated test in which a syntheticroad soil slurry is applied to the plated surface of an article and thearticle is then exposed to a warm humid atmosphere. A Corrodkote slurryformulation includes both soluble and insoluble elements and sufficientliquid to give proper spreading consistency. The slurry is applied tothe surface being tested by means of a paint brush, or similar device,to produce a fairly uniform coating, after which the coated specimen isexposed to specified humidity conditions.

A standard Corrodkote mixture, efiective in testmg chromium-nickelcombinations over steel, is:

Kaolin, grams 30 Ferric chloride, gram 0.165 Cupric nitrate, gram 0.035Ammonium chloride, gram 1 Water, ml. 50

The CASS test involves exposing the plated parts to a salt spraycontaining small concentrations of cupric chloride and acetic acid.

Both the Corrodkote and the CASS tests have been accepted by theindustry as well established accelerated tests for corrosion. For acomplete description of the tests see Plating, vol. 44, p. 763, 1957.

In some instances neither the Corrodkote test nor the CASS test areabsolutely reliable in predicting service life of plated parts on cars.When some plated panels are rated good by the Corrodkote test,-the samepanels are less highly rated by the CASS test and the reverse would beobserved with other plated panels. Therefore the test results set forthhereinafter to show the advantages of the present invention are obtainedby submitting the sample panels to 3 or 4 Corrodkote cycles, and insteadof using more Corrodkote cycles, further submitting the panels to theCASS test. Controls or panels for comparison are always employed. Arepresentative test would be 3 or 4 Corrodkote cycles plus 48 hours ofCASS exposure.

The advantage of using the triple-layer composite systems to protect acorrodible substrate becomes significant when reference is made to FIGS.13 of the drawing. These figures illustrate in sequence the progressivecorrosion of a typical three-layer composite. As a corrosion pit isformed in the top nickel layer as shown in FIG. 1 (usually through apore or other defect in the chromium decorative coat), the pitprogressively enlarges hemispherically. This corrosion site continuallyenlarges until it reaches the more anodic intermediate layer.

In FIG. 2 the corrosion pit has attacked the intermediate layer,progressed until the pit has become substantially cylindrical ratherthan hemispherical and has undercut the intermediate layer slightlybelow the top layer of nickel. Because the lower layer is more noblethan the two upper layers of nickel, the lower layer remains relativelyfree from corrosion.

As the intermediate layer corrodes beneath the top or upper layer, theintermediate layer becomes more inaccessible to the corrodingelectrolyte and the total polarization increases due to localizedchanges in concentration causing increase in the resistance of theelectrolyte and other ohmic eifects. Thus the rate of the corrosion ofthe intermediate layer decreases and the top layer begins to corrodeagain and exposes the intermediate layer renewing the anodic protectionof the top layer. This cycle continually is repeated while the lowerlayer is protected by the sacrificial action of both the intermediatelayer and the top layer. In FIG. 3 there is shown a plate with thecorrosion pit widened with the lower layer of nickel being attacked onlyvery slightly. The rate of corrosion of the lower layer in relation to ithe top and intermediate layer is usually less than 1 to 100.

In the triple-layer system the intermediate layer acts as thesacrificial anode primarily, while the top layer provides the brightsurface for the decorative chromium; the composition of the intermediatelayer need not be controlled as rigidly as the composition of the toplayer in a duplex system.

The reasons that the triple-layer systems of the present inventionmanifest such excellent corrosion resistance is not completelyunderstood. From a superficial study of the electrochemical propertiesof arsenic-containing nickel deposits, it is observed that the relativepotentials obtainable from theses deposits generally are higher thanthose obtainable from sulfur-containing nickel deposits, usually atleast millivolts, measured 5 percent sodium chloride solution adjustedto a pH of 3 with acetic acid. Thus, it appears that the intermediatelayer of the instant triple-layer composites is prepared consistentlyanodic to the upper and lower layers of nickel.

As mentioned hereinbefore, the triple-layer system is most effectivewhen the intermediate layer is anodic to the lower layer and the upperlayer and wherein the lower layer is cathodic to the upper layer.Supposedly the mechanism taking place is that the intermediate layeracts as a primary sacrificial anode and the upper layer acts as asecondary sacrificial anode, protecting the lower layer while theintermediate layer is temporarily less active. Moreover, the use ofarsenic as the alloying constituent with nickel in the preparation ofthe intermediate layer provides advantages other than that of providinghigher potentials than those obtainable from the use of sulfur as thealloying constituent with nickel.

In order to carry the present invention into effect, the substrate isplated first with a lower layer of nickel and then with the intermediatelayer of nickel and the upper layer of nickel. Any solution of nickelions designed for electroplating nickel may be used.

The solutions contain at least one of the following salts: nickelsulfate, nickel chloride, nickel fluoroborate and nickel sulfamate,wherein the solution is adjusted to an operating concentration ofnickel. Included among the various baths useful in carrying out thepresent invention are (1) the various barrel plating baths generallycomprising nickel sulfate and nickel chloride as the source of thenickel ion and buffer systems comprising boric acid alone or inconjunction with magnesium sulfate or ammonium chloride, (2) theall-chloride bath designed for use Where a high current density isdesired, comprising nickel chloride as the source of nickel ion andboric acid as the buffer, (3) the fluoroborate bath comprising nickelfluoroborate as the source of nickel ion and free boric acid as thebuffer alone or in combination with fluoroboric acid, (4) the commonWatts-type bath designed for all purpose nickel plating and generallycomprising nickel sulfate and nickel chloride as the source ofnickel ionbuffered with boric acid, (5) the all sulfamate bath comprising nickelsulfamate including boric acid as the buffer, (6) the chloride-sulfamatebath comprising nickel chloride and nickel sulfamate with boric acid asthe buffer and (7) other nickel baths made from nickel salts andcomplexing agents.

After the desired thickness is obtained for the first or lower layer ofnickel, the arsenic-containing intermediate layer of nickel isdeposited. An arsenic-supplying compound is added to one of the abovebaths adjusted to the appropriate concentration and a thin layer ofarseniccontaining nickel is deposited directly on the surface of thefirst or lower layer of nickel.

The composition is then completed by plating a third deposit of nickeldirectly on the surface of the intermediate plate. Normally this plateis fully bright to provide an optimum surface for the decorativechromium plate. The decorative chromium layer advantageously is fromabout 0.005 mil to about 0.2 mil thick. Each of the above layers ofnickel may be deposited using more than one step such as for example byinterrupting the plating cycle for one reason or another.

In its preferred form the composite coating of the present inventioncomprises a first or lower layer of ductile sulfur-free nickel. Thispreferred plate is deposited from a typical Watts-type orfluoroborate-type bath containing an effective amount of a sulfur-freeleveler such as coumarin and the like. The top layer of nickelpreferably being fully bright is deposited upon one of the above bathsusing a brightener of the first class (sulfo-oxygen carrier) and abrightener of the second class. Where the top layer is high in sulfurcontent (0.1 to 0.3 percent) the lower layer also may be deposited froma bath containing in addition to a brightener of the first class(sulfo-oxygen compound) small amounts of a brightener of the secondclass. The baths disclosed in US. Patent 3,090,733, as being useful forpreparing the upper layers of nickel in the composite disclosed andclaimed therein may be used to deposit the upper layers of nickel forthe present invention.

As indicated hereinbefore, the lower and top layers of nickel may bedeposited from baths of conventional compositions and in the baths theremay be present one or more brighteners of the first class. Thesecompounds generally comprise an aryl ring, a substituted aryl ring or anunsaturated aliphatic chain with a sulfur-containing radical in the formof sulfonic acids, sulfonates, sulfonamides, sulfimides, sulfinic aacidand sulfones. The aryl ring advantageously may be derived from benzene,naphthalene and the like, the substituted aryl ring may be derived fromtoluene, xylene, naphthylamine, toluidine, benzyl naphthalene and thelike and the alkylene chain may advantageously be derived from vinylcompounds or allyl compounds and the like. Examples of sulfo-oxygencompounds of the above described type and which are useful particularlyin the instant nickel plating baths are found in US. Patents 2,757,133and 2,766,284.

Almost uniformly, the top layer of nickel is deposited from bathscontaining, in addition to brighteners of the first class, brightenersof the second class including organic compounds dependent on thecarbonyl C=O) radical for the brightening action such as the variousketones, aldehydes, carboxylic acids, some proteins (gelatin) and thelike; those compounds dependent on the ethylenic (CH=CH--) radical forthe brightening action such as the alkylenic carboxylic esters, thealkylenic aldehydes, the aromatic compounds dependent on the in-ringethylenic radical such as the aryl aldehydes, the sulfonated arylaldehydes, allyl and vinyl substituted compounds, coumarin and itsderivatives, and the like; those compounds dependent on the acetylenicradical including the acetylenic alcohols, nitrogen heterocyclics havingan N-substituted acetylenic radical and the like; those compoundsdepending on the azo and azine type nuclei @N- and N=N) for thebrightening action such as the azine, thiazane and oxazine dyes, thetriphenyl methane dyes, the quinidines, pyrimidines, pyrazoles andimidazoles, the pyridinium and quinolinium compounds, and the like;those compounds dependent on the cyano radical for the brighteningaction such as the nitriles, thionitriles and the like; and thosecompounds dependent on the thiuoreide radical (NC=S) such as the cyclicthioureides and thiourea.

Compounds considered useful as brighteners of the second class includethe water-soluble acetylenic compounds set forth in US. Patent (Kardoset al.) 2,712,522; the aryl, alkylene and arylalkynoxy sulfonic acidsset forth in US. Patent 2,800,442; the alkynoxy sulfonic and carboxylicacids having the triple bond separated from the acid radical by at leastone oxygen atom set forth in US. Patent 2,841,602; and the nitriles setforth in US. Patents 2,524,010; 2,647,866; 2,882,208; 2,978,391 and3,093,557.

Where cobalt is desired as an alloying constituent in the nickel layersthe instant bath may be adjusted by adding any of the cobalt salts wellknown to those skilled in the art. For example, the halides of cobaltare particularly useful including cobalt chloride, cobalt bromide, andthe like. Cobalt sulfate may be used also.

Nickel electroplating baths particularly useful in combination withthese brightener systems include the Wattstype and fiuoroborate-typebaths having increased nickel content. Such baths are designed for usewith organic brighteners in general; they may be operated at the highercurrent densities desirable for the effective use of the organicbrighteners. The preferred Watts-type bath essentially comprises anoverall nickel content ranging from 70 to 115 grams per liter providedby 270 grams per liter to about 450 grams -per liter of nickel sulfateand from about 20 grams per liter to about grams per liter of nickelchloride with about 30 to 40 grams per liter of boric acid as the bufferand the preferred fiuoroboratetype bath essentially comprises anover-all nickel content ranging from 75 to grams per liter provided byabout 440 grams per liter of nickel fiuoroborate with about 30 grams perliter of boric acid as the buffer.

For purposes of the present invention, boric acid is preferred as thebuffer-as an additive to maintain the desired pH. However, acetic acid,borax (sodium tetraborate), formic acid, the fiuoroborates, and othercompounds commonly known to have utility as buffers, may be used withthe baths of the present invention with no apparent undesirable efiects.

Illustrative examples of Wetting agents which may be employed in thebaths for carrying out the present invention include a great majority ofthe anionic surfactants. The sulfate type particularly may be used.Included among this type are certain of the alkylsulfates,aralkylsulfates, alkylsulfonates, and the aralkylsulfonates. Trisulfonylmethanes such as tri(hexylsulfonyl)methane, tri(heptylsulfonyl) methaneand the like may be used effectively also as wetting agents.

The use of a wetting agent in baths used in carrying out the presentinvention is optional; excellent deposits are obtained from baths havingno wetting agent provided they are free of Water-insoluble andhydrophobic matter.

The preparation of the arsenic-nickel plating baths advantageously iscarried out merely by adding from about 0.05 gram per liter to about 5.0gram per liter and'preferably 0.5 gram per liter to about 2 grams perliter of an arsenic-supplying compound to any one of the aboveenumerated baths used for depositing nickel. The amounts of theparticular arsenic-supplying compound necessary to impart a desiredamount of arsenic in the nickel deposit vary with each compound; and, ofcourse, with the temperature of the bath and cathode current density.Moreover, many arsenic-containing compounds which can be used to impartarsenic into the nickel deposit are not very soluble in water whichtherefore restricts or limits 7 the amounts which can be used.

Preferably, the operating temperature of a typical bath (Watts-type) isin the range of from about F. to about F. This range is not critical;however good deposits may be obtained at temperatures as low as 50 F. orlower and at temperatures as high as F. or even at the boiling point ofthe electrolyte. The arsenic compounds particularly useful are thosewhich are capable of supplying arsenic in a form which permitscodeposition of arsenic with the nickel, preferably those compoundscapable of supplying arsenite ions or other trivalent arsenic ions.

The operative current density at the cathode is dependent also on theoperating current density for the chosen bath composition free fromarsenic. Where the Wattstype bath is employed, current densities rangingfrom about 10 to 50 amperes per square foot are preferred.

When using acid nickel baths the arsenic-containing nickel deposits areplated more advantageously from baths having lower pH values. Broadlythe pH should be in the range of from 1.5 to and preferably in the rangeof from 2 to 4.

For purposes of the present invention, the arsenic com- 3 large amountsof arsenic but manifested proportionately low anodic potentials whencompared to nickel deposits using the arsenites and having similararsenic concentrations.

pounds which may be used most effectively in forming the 5 The reasonsfor this disparity in the relative potentials arsenic-containingintermediate layers are those comof nickel deposits obtained usingarsenates is not clear. pounds capable of supplying arsenite ions to thebath One possible explanation for this difference in electrosuch asarsenious oxide (arsenic trioxide) and arsenious chemical activitybetween nickel deposits is that the acid, the alkali metal arsenites,nickel arsenite and cobalt arsenic contained in the deposits from bathsusing the arsenite and the dilute acid-soluble alkaline earth metalarsenate largely is present in an occluded form, possibly arsenites,such as calcium arsenite and strontium arsenite. unchanged arsenate. Thenickel deposits manifesting Hydrolyzable compounds of arsenic may alsobe uwd adhigh anodic potentials (much higher than those obtainedvantageously such as, for example, arsenious chloride using arsenates)probably have the arsenic present as (arsenic trichloride). Generallythis class of compounds nickel arsenide. When the arsenic is obtained inthe plate includes substantially all of the compounds capable of in thisform, there is very little advantage in having more hydrolyzing to formarsenious acid. than about 4 percent arsenic in the deposit.

The organic esters of arsenious acid including both the While thearsenates in general are less desirable as a fully substituted andpartially substituted esters may be source of arsenic in the bath, goodcorrosion results have used if they are sufiiciently water soluble orhydrolyze to been obtained from composites made using certainarsearseniou-s acid or other water soluble compounds. These nates orother pentavalent arsenic compounds. Allyl esters generally may berepresented by the following arsonic acid particularly gives goodresults, in many ingeneral formula: stances as good as the resultsobtained using sodium arsenite as the source of arsenic.

(R nAS {OR1)3n P'henyl arsonic acid and benzylarsonic acid are ad-Wherein is an integer from O to zlnelllsive, R is a Inemvantageouslyused as the arsenic-supplying compound. Selected from the group hlg ofhydroge lkyl, (See US. Patent 2,211,535.) Organic arsenic compounds arylalkaryl hydroxyarylane-th111w and a member containing a triple bond suchas propargyl arsonic acid selected from the group consisting ofhydrogen, a monoand .butyne arsenic acid also may be used valeriiimetal.g g aryl hydroxyalkyand Wlth As a further refinement of the presentinvention a sul'foprovision is or 1 may represent a Walent .meta oxygencompound or brightener of the first class is added atom, an alkanylene,alkenylene, arylene and substituted h t b n t P f divalent organicradicals. In this instance R represents to t e arsenic C on ammg m smaamoun a single divalent radical bridging two oxygen atoms, conably thearsemc 1s pres,ent the: baths arsemte, i nficbsd directly to the arsenicatom. or any other form WhlCh W111 provide ions containing Examples ofsome Specific compounds represented by trivalent arsenic. Thesulfo-oxygen compound surpris- Formula I include the trialkyl esters ofarsenious acid ingly acts to Provide a semi-bflght to a y P such as thetrimethyl, triethyl, triisopropyl derivatives; Pending 011 the amount ofarsenic Present in the deposit the triaryl esters of arsenious a id suchas th triphenyl Whereas for similar arsenic concentrations a dark toblack esters; the :mixed alkyl and and triesters of arsenious aciddeposit is obtained without the sulfo-oxygen carrier. The such asethylphenylene arsenite; the organic substituted 40 concentrations ofthe sulfo-oxygen carrier useful in overarsenious acids such as hisphenyl) arsenious acid, hycoming the blackening of 'the depositgenerally are similar droxyphenylphenyl arsenious acid, ethylphenylarsenious to the concentrations useful with arsenic-free baths. Fromacid and the like; and the diesters having a hydrocarbon about 0.5 gramper liter to about 2 gnams per liter of the radical connected directlyto the arsenic atom such as for sulfo-oxygen compound cover effectiveamounts but example dibutoxyphenyl arsine. amounts outside this rangeare useful also.

Generally these organic derivatives are limitedly soluble It has beenfound that relatively small amounts of sulfur in Water and offer oadvantage over th very wat are imparted into the deposit; an amountwhich is much soluble arsenious acid and the metal arsenite salts. lessthan is obtained in the deposit using a fully bright The arsenates maybe used also but the composites nickel bath containing a brightener ofthe second class. made using the arsenates often act erratically whentested The following Table A sets forth specific compositions forcorrosion properties; the amounts of arsenic deposited of baths usefulfor depositing the lower layer in preparing with the nickel from bathscontaining arsenates do not the triple-layer composite electroplate ofthe present inafiipear to be correlata'ble with the relative potentialsof the vention.

TABLE A Boric Bath Nickel Salts, g./l Addition Agent, g./l. OtherAdditives, g./l. Wetting Agents, g./1. Big; pH

1a {fiiefikhiiqail Sodium lauryl sulfate, 0.02. 37 3. 5 2a }Ooumarin,0.2 Formaldehyde (40%), 0.1 c.c./1 do 37 4. 0

NiSO4.6Hz0,3O0 3a {NiClz.6H20, 45 }Nickel Formate, 4.5 Formaldehyde, 0.5cc./ 30 2. 5 00804-61120, 30 v 4a. {i%?: q 6q: }3 Bromocoumarin, 0.2 304. 0 5a {ifilf f fif fi}: }Butynediol, 0.1 Chlora1,0.05 30 4.0 w{asaaaat acumen, {aaaaaiaaainae: podium 35 7a 39 }Ooumarin, 0.2 Chloral,0.05 do 35 3. 5

deposit. In many instances deposits from baths containing derivatives ofarsenic pentoxide contained relatively The following Table B sets forthspecific compositions of baths useful for depositing an upper layer ortop layer in preparing the triple-layer composite electroplate of thepresent invention:

10 Three panels per Examples I VIII were submitted to the CorrodkoteTest for 80 hours and to the CASS test for 48 hours.

TABLE B Boric Ex. Nickel Salts, g./l. Organic Sulfa-oxygen cpd., g./l.Brighteners, g./l. Wetting Agents, g./l. Acid pH N0. Buffer,

1b lNaphthalenedisulfonic acid, 4. Reduced fuchsin, .007 Sodium laurylsulfate, 0.03-. 37 3. 5

NiSO- GH2O 3O Saccharin, 1--- Butynediol, 0.2. iNgonenzofaz. Allylsulfonate, Coumariu, 0.1.. 37 3b.. Dibenzenesulfonimide, 3.-..Allylpyridinium bromide, 0.05 .do 37 4. 0 4b {i%)16}l[ 6O,3Z:/00. }p,poziygbgs(dibenzenesullon- B,B thiodipropionitrile, 0.003--. Sodium oetylsulfate, 0.1 37 4. 0

"" 1 2 ami e NlSO4.6HzO, 150. Saecharin, 2 Nronerno, 150 Allylsulionate, 1. 37 5 6b j g }Same as 2D e s 211 Same as 37 4.0 7b.....{}%gfgf%gi9 }Benzenesullouamide, 2- -.d0 37 3. 5

The panels of Examples I-VIII remained substantially unattacked,manifesting no rust spots.

By comparison the same bath and conditions were used to plate anotherseries of steel panels using varying amounts of sodium benzenesulfinatein the bath used to deposit the intermediate layer. The thickness of thenickel layers for each panel and the amounts of the sodium benzenesulfinate used in the bath are set forth in the following table.

The following examples set forth the preparation of compositeelectroplates according to the present invention. Example I Using bathZn from Table A, a 0.45 mil layer of nickel was deposited on steelpanels. The coated panel was rinsed with water and a 0.13 mil layer ofnickel was deposited from the following bath at a current density of 40amps/sq. ft. The bath was kept at a temperature of about 140 F. and a pHof about 4.0. C stitue t A t TABLE III.THICKNESS OF LAYER IN MILS NiSO-6H O, g./l. 300 NiCl '6I-I O, g./l. 45 .?mgunt H3BO4, g./ 41 ExampleNo. Lower Inter- Upper b r z ie NaAgo g /1, 1 ed ate sulfiraate Wettingagent, cc./l. 3 fis i f F f The arsenic in the plate had about 2.0percent by weight based on the total weight of the second orintermediate .45 07 .37 4 layer. 1%?) 8? i The panel was rinsed againand a 0.55 mil top or upper .50 10 .57 4 layer of bright nickel wasdeposited from bath 4b of 1%? :93 :23 :2 Table B. .45 07 .46 .5

After rinsing again, a 10-12 millionths of an inch coat :2; fig 12. 3 ofchromium was plated on the surface of the upper layer. .ig 1 8 .32Examples Il-VIII I 12 14s is Using the same baths and conditions as wereused in Example I, a series of steel panels was coated with three Thefollowing Table IV sets forth corrosion tests relayers of nickel and alayer of chromium. The thicksults of the panels of Table III.

1168868 Of each layer are set forth in the following Table TABLE IV NORUST SPOTS OBSERVED AFTER COR I. The amount of arsensic in theintermediate layer of DK T YCLE each was about 2.0 percent by weightbased on the weight of the intermediate layer. Example N o. 1 2 3 40.45s 2 TABLE I.THICKNESS OF LAYER IN MILS 13 31 51 62 02 Example No.Lower Intermediate Upper 0 2 2 5 18 0 7 21 09 0 2 6 14 20 0.47 0.13 0.530 0 1 22 45 0.45 0.15 0.45 0 3 1s 34 58 0.45 0.12 0.46 1 12 45 53 830.45 0 .12 0 .46 0 1 21 40 58 0.50 0.10 0.52 2 3 20 a9 72 8 43 3g 66 274 54 The same bath and conditlons were used to plate an- 3 21 34 36 51other series of steel panels except 1.27 grams per liter of allylarsonic acid was substituted for the sodium arsenite in the bath usedfor plating the intermediate layer.

The thicknesses of each layer are set forth in the following Table II.The amount of arsenic in the intermediate layer of each sample was about2 percent by weight based on the total weight of the intermediate layer.

TABLE II.THICKNESS OF LAYER IN MILS 70 Each cycle equals 20 hoursexposure. 48 hours.

Duplex (double layer) nickel panels, plated frornthe same baths as citedabove for the bottom and top layers, under the same conditions, wereCorrodkote-CASS tested and showed 38 to 100+ rust spots.

Example XXI Lowe Inwmediate Using the bath of Example I with one gramper liter of saccharine added thereto, panels are coated accord- ExampleNo. Upper VII..

81%; gig ing to the procedure outlined in Example I. The sodium arsenite(NaAsO concentrations are adjusted in the bath from 0.5 gram per literto 3.0 grams per liter using increments of 0.5 gram per liter. Thenickel deposited from the baths containing the different concentrationsof sodium arsenite range from being semi-bright to a metallic graycolor. The corrosion resistance of each of the composites is comparableto those obtained according to Examples I through VIII. The semi-brightand metallic gray deposits are in definite contrast with the blackdeposits obtained from baths not using saccharine where the amount ofsodium arsenite in the bath exceeds 2.5 grams per liter.

The present invention in its broadest form includes composites orlaminates of nickel layers having more than three layers of nickel andcomposites or laminates wherein the arsenic-containing nickel layer issandwiched between layers of nickel which may have relative potentialsequal substantially to each other or be slightly more cathodic than theintermediate layer.

Where the composite has more than three layers of nickel, thearsenic-containing nickel layer is always bonded to layers of nickel onboth sides. Moreover, at least one of the nickel layers should becathodic to the arsenic-containing layer and be substantially free fromarsenic, phosphorus, sulphur and substantially all other nickel alloyingconstituents.

Examples of systems for the composites of the present invention includecomposites having, in addition to those already described, (1) asulfur-free lower layer and a sulfur-free upper layer, (2) a brightlower layer and a bright upper layer and (3) a sulfur-containing lowerlayer and a sulfur-containing upper layer. Thus it is easily understoodthat composites may be made according to the present invention where thelower layer contains from to about 0.15 percent sulfur and'the upperlayer contains from 0 to about 0.4 percent sulfur. Higher amounts ofsulfur can be obtained in the nickel deposits but there is no advantagein using the higher amounts (1.0 percent) of sulfur.

While specific examples of the invention have been set forthhereinabove, it is not intended that the invention be limited solelythereto, but to include all of the variations and modifications fallingwithin the scope of the appended claims.

What is claimed is:

1. As an article of manufacture a laminate comprising three firmlybonded layers of nickel including an intermediate layer of anickel-arsenic alloy sandwiched between and in adherent contact with anarsenic-free lower lower layer of nickel and an arsenic-free upper layerof nickel, said nickel-arsenic alloy consisting essentially of nickeland about 0.025 percent to about 8.0 percent arsenic.

2. As an article of manufacture a laminate comprising three firmlybonded layers of nickel including an intermediate layer of anickel-arsenic alloy sandwiched between and in adherent contact with arelatively noble lower nickel-containing layer and a top layer of brightnickel anodic to said lower layer, said alloy consisting essentially ofnickel and from about .025 percent to about 8 percent by weight arsenicand being anodic to said lower layer and said top layer.

3. As an article of manufacture a composite coating bonded to a metalsubstrate susceptible to atmospheric corrosion comprising as itsessential layers three adjacently bonded layers of electrodeposits, thelower layer of which consists essentially of a nickel electrodeposithaving from 0 to about 25 percent cobalt by weight therewith and anaverage sulfur content of less than 0.15 percent by weight based on theweight of said electrodeposit, a top layer of which consists essentiallyof a bright nickel electrodeposit having from 0 to about 50 percentcobalt alloyed therewith and from about 0.03 percent to about 0.4percent sulfur by weight and the intermediate layer of which consistsessentially of a nickel alloy electrodeposit having from 0 to 25 percentcobalt alloyed therewith and also 12 having alloyed therewith from about0.25 percent to about 4 percent arsenic based on the total weight ofsaid electrodeposit.

4. The article of claim 3 wherein, said lower layer has a thickness offrom about 0.3 mil to about 2 mils, said top layer has a thickness fromabout 0.15 mil to about 1 mil and said intermediate layer has athickness ranging from about 0.01 mil to about 0.2 mil.

5. As an article of manufacture a composite coating bonded to a metalsubstrate comprising as its essential layers three adjacently bondedlayers of nickel, the lower layer of which consists essentially ofnickel deposits having a sulfur content of less than about 0.15 percentselected from the group consisting of nickel and a nickelcobalt alloycontaining less than about 25 percent cobalt based on the weight of saidlower layer, the upper layer of which consists essentially of nickeldeposits having a sulfur content of from about 0.03 percent to about 0.4percent, selected from the group consisting of nickel and anickel-cobalt alloy containing less than about 50 percent cobalt basedon the weight of said upper layer and the intermediate layer of whichconsists essentially of a deposit selected from the group consisting ofa nickelarsenic alloy consisting essentially of from about 0.25 percentto about 4 percent arsenic and a nickel-cobalt arsenic alloy consistingessentially of from about 0.25 percent to about 4 percent arseniccontaining less than 25 percent cobalt, the remainder being nickel.

6. As an article of manufacture a composite coating bonded to a metalsubstrate selected from the group consisting of iron, steel, copper,zinc, aluminum, magnesium and alloys thereof comprising as its essentiallayers three adjacently bonded layers of electrodeposits, the lowerlayer of which consists essentially of nickel electrodeposits havingfrom 0 to about 25 percent cobalt by weight alloyed therewith and anaverage sulfur content of less than about 0.15 percent by weight basedon the weight of said electrodeposit, a top layer of which consistsessentially of a bright nickel electrodeposit having from 0 to about 50percent cobalt alloyed therewith and from about 0.03 percent to about0.4 percent sulfur by weight and a nickel alloy intermediate layerconsisting essentially of from 0 to 25 percent cobalt and from about0.25 percent to about 4 percent arsenic based on the total weight ofsaid intermediate layer.

7. The article of claim 3 wherein said top layer of nickel iselectroplated with a chromium deposit having a thickness ranging fromabout 0.005 to about 0.2 mil.

8. In a method of electroplating from aqueous solutions acorrosion-protective composite nickel coating comprising as itsessential layers three adjacently bonded layers of electrodeposits on ametal surface susceptible to atmospheric corrosion wherein a lower layeris cathodic to an intermediate layer and an upper layer and saidintermediate layer is anodic to said lower layer and said upper layer,the improvement consisting essentially of electrodepositing saidintermediate layer from an aqueous solution of nickel salts andcompounds capable of permitting codeposition of arsenic with the nickelto form a layer of nickel having a thickness of from about 0.01 to 0.2mil and an arsenic content of from about .025 percent to about 8 percentby weight of the intermediate layer.

9. The method of claim 8 wherein said lower layer is deposited from anaqueous solution comprising nickel salts and at least one sulfurcompound to provide a layer consisting essentially of nickelelectroplate having from 0 to about 25 percent cobalt by weight alloyedtherewith and an average sulfur content up to about 0.15 percent byweight, and wherein said top layer is deposited from an aqueous solutioncomprising nickel salts and sulfur comprises a bright nickelelectroplate having from about 0.03 percent to about 0.4 percent sulfurby weight and the intermediate layer of which consists essentially of adeposit of nickel containing from about 0.25 percent to about 4.0percent arsenic based on the total weight of said intermediate layer.

10. The method of claim 8 wherein said lower layer is deposited from asulfur-free aqueous acid solution comprising nickel salts and at leastone sulfur-free compound capable of leveling action and wherein said toplayer comprises a bright nickel plate having from about 0.03 percent toabout 0.4 percent sulfur by weight and said intermediate layer consistsessentially of a deposit of nickel containing from about 0.25 percent toabout 4.0 percent arsenic based on the total weight of said intermediatelayer.

11. The method of claim 10 wherein said compound capable of levelingaction is coumarin.

12. The method of claim 8 wherein said intermediate nickel layer isplated from an aqueous ac'dic bath containing from about 0.5 gram perliter to about grams per liter of a compound capable of supplying triplevalent arsenic ions.

13. The method of claim 8 wherein said intermediate nickel layer isplated from an aqueous acidic bath containing from about 0.5 gram perliter to about 5 grams per liter of a compound capable of supplyingpentavalent arsenic ions.

14. The method of claim 12 wherein said intermediate layer is platedfrom an aqueous nickel plating 'bath containing from about 1.0 gram perliter to about 8 grams per liter of a compound capable of supplyingarsenic to said bath in a form which permits codeposition of saidarsenic with said nickel.

15. A method of electroplating from an aqueous solution a corrosionprotective composite coating on a metal surface susceptible toatmospheric corrosion which comprises the'steps of (1) electroplating onsaid surface in at least one electroplating step an adherent layerconsisting essentially of nickel having a thickness of about 0.3 mil toabout 2.0 mils and a sulfur content of less than about 0.15 percent, toform an adherent lower layer, (2) electroplating directly on said lowerlayer in at least one plating step an adherent intermediate layerconsisting essentially of a plate selected from the group consisting ofnickel plate and nickel-cobalt alloy plate containing at least about 75percent nickel, said intermediate layer having a thickness of about 0.01mil to about 0.2 mil and an arsenic content of about 0.25 percent toabout 4 percent, (3) electroplating directly on said intermediate nickellayer an adherent upper layer in at least one electroplating stepconsisting essentially of an electroplate selected from the groupconsisting of nickel electroplate and nickel-cobalt alloy electroplatecontaining at least about 50 percent nickel, said upper layer having athickness of about 0.15 to about 1 mil and an average sulfur content of0.03 to 0.3 percent, said upper nickel layer containing a higherpercentage of sulfur than said lower layer.

16. The method of claim 15' wherein said intermediate layer is platedfrom an aqueous acidic nickel bath containing from about 0.5 gram perliter to about 15 grams per liter of a water-soluble compound capable ofsupplying arsenic in a form which permits codeposition of said arsenicwith said nickel.

17. In a method of electroplating from aqueous solutions acorrosion-protective composite coating comprising as its essentiallayers three adjacently bonded layers of nickel electrodeposits on ametal substrate susceptible to atmospheric corrosion wherein a lowerlayer is cathodic to an intermediate layer and an upper layer and saidintermediate layer is anodic to said lower layer and said upper layer,the improvement comprising electrodepositing said intermediate layer ofnickel from an aqueous acid solution of nickel salts, sulfo-oxygencompound and at least one compound capable of supplying arsenic in aform which permits codeposition of arsenic with the nickel to form alayer of nickel having a thickness of from about 0.01 mil to about 0.2mil and an arsenic content of from about 0.025 percent to about 8percent based on the weight of said intermediate layer.

18. The method of claim 17 wherein said lower layer is deposited from asulfur-free aqueous acid solution comprising nickel salts and at leastone sulfur-free compound capable of leveling action and wherein said toplayer comprises a bright nickel plate having from about 0.03 percent toabout 0.4 percent sulfur by weight and said intermediate layer comprisesa deposit of nickel containing from about 0.25 percent to about 4.0percent arsenic based on the total Weight of said intermediate layer.

19. The method of claim 17 wherein said intermediate nickel layer isplated from an aqueous acidic bath containing from about 0.5 gram perliter to about 5 grams per liter of a compound capable of supplyingarsenite ions to a bath and a sulfo-oxygen carrier.

20. The method of claim 19 wherein said compound is sodium arsenite andsaid sulfo-oxygen carrier is saccharine.

References Cited by the Examiner UNITED STATES PATENTS 3,090,733 5/1963Brown 29-19616 HYLAND BIZOT, Primary Examiner.

1. AS AN ARTICLE OF MANUFACTURE A LAMINATE COMPRISING THREE FIRMLY BONDED LAYERS OF NICKEL INCLUDING AN INTERMEDIATE LAYER OF A NICKEL-ARSENIC ALLOY SANDWICHED BETWEEN AND IN ADHERENT CONTACT WITH AN ARSENIC-FREE LOWER LAYER OF NICKEL AND AN ARSENIC-FREE UPPER LAYER OF NICKEL, SAID NICKEL-ARSENIC ALLOY CONSISTING ESSENTIALLY OF NICKEL AND ABOUT 0.025 PERCENT TO ABOUT 8.0 PERCENT ARSENIC. 